7.3 kW Bi Facial Rooftop Panels: ~7 year ROI: Fact OR fiction?

pinnks

As a slight aside, and if the OP is looking to max out on the green aspects of any install, does anyone know what (if anything) happened with combined PV/thermal panels? I recall having read that they were the next new kid on the block when I was looking to install. The theory being that the solar thermal mops up the residual heat form the PV, which in turn keeps them cooler and more efficient.

Haven't heard anything on this subject for years.

michaels

Screwdriva wrote: »

Many thanks - I've deleted the iBoost per your suggestions. It's £250 reduced from the total, which helps if other users here have not seen 3 digit annual savings, which is what the installers claim for their client base.

This now makes all system components warranted for 25 years including labour. Total cost, 6900/- all in.

Don't forget with no iboost own use falls by 1000kwh per year with export up by the same amount. Given iboost units are worth at most 6p and you are estimating 7p for export this must make sense but please try to understand the calcs or you will be a miss selling claim after the first 12 months.

mnbvcxz

pinnks wrote: »

As a slight aside, does anyone know what (if anything) happened with combined PV/thermal panels?

I'm going to make a complete guess that they were done in by the cost of plumbing.

Screwdriva

Martyn1981 wrote: »

Can I just say (politely) that I'm not entirely convinced by the bi-facial idea and associated costs, as I've stated previously, but since you are going down that route, it would be really great if you could keep us all informed going forward.

This thread, resurrected periodically would work, or if you really want to get obsessive, like so many of us, there is the thread for chatting about generation:

I got that impression, yes I hope that the system does indeed outperform and exceeds expectations all around. I'll be sure to circle back with quarterly updates.

Screwdriva

Scaffolding is up. Image of rooftop can be seen here . Our goal is to maximize the number of panels on the South facing roof while avoiding the shadow of the chimney.We're hoping to fit 6 on that roof.

Any last minute advice is more than welcome!

michaels

Screwdriva wrote: »

Scaffolding is up. Image of rooftop can be seen here . Our goal is to maximize the number of panels on the South facing roof while avoiding the shadow of the chimney.We're hoping to fit 6 on that roof.

Any last minute advice is more than welcome!

Are you putting the on the W SW aspect too - plenty of space there and they give you power later in the day which might be more useful for own use / more valuable for time of day export tariff and means that the 3.68kw dno cap is less of an issue if you go over 4kwp of panels as the different aspects are peak power at different times. With different aspects they either need to be on separate strings or use the micro invertors.

Screwdriva

That's the plan. Ideally 6 panels on the South and the remaining on the West side unless it makes more sense to split between East/ West roofs.

Sterlingtimes

After 5 years, the benefit of my iBoost is approximately zero. The value of exported electricity is 5.38 pence per kWh. The water heating efficiency of my boiler is no greater than 50%. So each kWh of gas costs .0321/0.5 = 6.42 pence per kWh. My annual saving is approximately £7.00.

ABrass

East/west would be better for an oversized system, as you have. That way you'll generate more through the morning and evening. Midday during the summer you'll max out your inverter without question, so you want to stretch that peak out so you get the most total power and spread out over the maximum of the day.

Screwdriva

LG400N2T Panels & P505 SE optimizers have arrived. They're massive! After some measurements of the roof, we've arrived at the following:

6 panels on the South facing roof with 1 panel expected to partially shade thanks to the chimney (see pic)
2 Panels each on the West and East facing roof to extend generation for the longest duration.

The panels are transparent, so the solar reflective paint is clearly visible through them. If its visible, it will reflect to the rear of the panel, which will lead to added generation.